Abstract

Question

In adults with chronic constipation, is daily use of polyethylene glycol (PEG) for
6 months effective and safe?

Methods

Design: Randomized placebo-controlled trial.

Allocation: Unclear allocation concealment.*

Blinding: Blinded (unclear which groups were blinded).*

Follow-up period: 6 months.

Setting: 50 centers in the United States.

Patients: 306 patients with chronic constipation over the past 3 months (< 3 satisfactory
stools per wk without laxative use and ≥ 1 of the following Rome criteria: straining,
lumpy or hard stools, or sensation of incomplete evacuation in > 25% of
defecations) and during a 14-day observation period (< 3 satisfactory bowel
movements per wk). Exclusion criteria were prior or current treatment with or sensitivity
to study medication; use of medications affecting bowel function; the irritable bowel
syndrome; pregnancy or lactation; past gastrointestinal (GI) surgery; known or suspected
GI obstruction; ileus; ascites; or chronic bowel, liver, or cardiopulmonary disorders.

Intervention: PEG, 17 g (n = 204), or placebo (n = 100) to be mixed in 8 oz of juice or other beverage and taken daily.

Outcomes: Overall treatment success (≥ 50% of treatment weeks with ≥ 3 satisfactory
stools, no use of rescue laxatives, and ≤ 1 of the following in > 25%
of defecations: straining, lumpy or hard stools, or sensation of incomplete evacuation).
Secondary outcomes included “super efficacy,” defined as 1 week with no constipation
symptoms (Rome criteria) and no use of rescue laxatives; and adverse events.

Patient follow-up: 99% (mean age 53 y, 85% women) were included in the intention-to-treat analysis. 170
patients completed all 6 months of the study.

Main results

More patients in the PEG group than in the placebo group had overall treatment success
(Table). The mean number of weeks that patients met the criteria for treatment success
and for super efficacy was higher in the PEG group (12 vs 3.4 wk and 9.2 vs 2.2 wk,
respectively, P < 0.001 for both). GI complaints were more common with PEG (40% vs 25%, P = 0.015); groups did not differ for other adverse effects.

Conclusion

In adults with chronic constipation, daily polyethylene glycol over 6 months reduced
constipation more than placebo.

†Abbreviations defined in Glossary. RBI, NNT, and CI calculated from data in article.‡≥ 50% of treatment weeks with ≥ 3 satisfactory stools, no use of rescue
laxatives, and ≤ 1 of the following Rome criteria in > 25% of defecations:
straining, lumpy or hard stools, or sensation of incomplete evacuation.

Commentary

The study by DiPalma and colleagues provides good evidence that PEG can safely relieve
chronic constipation in a select group of adults. The authors compared PEG with placebo,
rather than other forms of constipation, treatment and required that study patients
refrain from taking extra fiber, a commonly recommended intervention. The study confirms
that long-term use of PEG will not affect serum electrolytes, and the side effect
profile appears acceptable.

The findings may not extrapolate, however, to other types of patients. The average
duration of constipation was > 23 years for the study population, and the
study excluded people with such common, chronic illnesses as the irritable bowel syndrome
or cardiopulmonary disease. Also excluded were patients taking narcotics, such as
those who required palliative care. A recent Cochrane review (1) of constipation treatment in patients receiving palliative care found insufficient
data from randomized controlled trials, with too few comparisons of laxatives.

The study by DiPalma and colleagues provides excellent evidence that PEG is safe and
effective compared with placebo. Head-to-head comparisons with other regimens would
be welcome.

Alexander Chessman, MDMedical University of South CarolinaCharleston, South Carolina, USA